Those engaged in the art know that a producing well consists of casing inside of which runs a drill string and drill stems and further in, concentrically, a liner, which is the inside casing of the well.
When a packer is lowered to be seated in the producing well, particularly if the well slopes steeply, it is very difficult to guide the packer into the inside casing of the well, since the diameter of the latter is small. To lower the packer without allowing the packer to touch the top of the inside casing, which might not only damage such inside casing top, but also very often the packer itself is provided with outside rubber sealing parts, tends to slow up the lowering of the packer and also raises the cost of such action, owing to such equipment having to be replaced or reconditioned.
Practice has been to employ various kinds of centralizers, all of them meant to be employed within the actual casing. Such state of the art packers are, for instance, provided with pairs of collar-like parts spaced axially apart, usually made up by two interconnecting rings so as to enable the collars to be placed tightly within the casing but so as to slide therein. Such collars, lying axially apart, are rigidly connected to the opposite ends of the outside bowed portions of the blade-like parts that lie spaced out around the outside of said collars. The outer bowed portion of such blades fit into the drill hole and are squeezed inwardly when so fitting, and thereby exert a centralizing force upon the casing within which the packer is introduced.
Other types of packers consist of many sets of both short and long arms which stretch outwards to become a protruding elbow, which elbow has a follower meant to touch the drill hole of the well around it.
However the centralizers of the kinds referred to above are employed to centralize equipment inside the casing, and are in direct touch with such casing by means of their bowed blades and arms, but do not protect the top of the inside casing, particularly when very sloping wells are being worked.